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Inlets

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Inlets

It is the most critical heated zone where the sample must be introduced as a vapor into the carrier gas stream.

The most common Inlets are Injection Ports Sampling Valves

Liquid samples, in micro-liter volume, are usually injected by a special syringe through a silicon rapper septum onto the heated block, the sample is vaporized '' and carried into the column by the carrier gas stream. As for gas samples, the injector may be used, but only for qualitative analyses not for quantitative analyses, a special gas tight syringe is used for such a kind of this analysis. For quantitative identifications, a Gas Sample Valve (GSV) must be used.

Operating Procedures

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A. Injection Ports

(a) Handle gas or liquid samples. (b) Often heated to vaporize liquid samples. (c) The design and choice of injection ports

depends on the column

Diameter Type

Note:

Liquid or gas syringes are used to inject the sample through a septum into the carrier gas stream.

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Inlet Type Gas Control

1. Split/Splitless

Injector

2. Purged Packed

Injector

3. Cool On-Column

Injector

4. Programmed

Temperature

Vaporization (PTV)

5. Volatiles Interface

(VI)

EPC and Non-

EPC

EPC and Non-

EPC

EPC only

EPC only

EPC only

Inlet Types

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Inlet Types

Inlet Type Description

1. Split/Splitless Injector

It is called capillary injector as it is used only with capillary columns.

NoteThere are four injection modes: (a) Split Mode Major component analysis (High Concentration) (b) Splitless Mode Trace component analysis (Low Concentration) (c) Pulsed-Split Mode Allows larger injection volume (d) Pulsed-Splitless Mode Allows larger injection volume Faster sample transfer to column Less breakdown/Adsorption

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Split/Splitless Injector

Septum

Liner O-Ring

Liner

Washer/Seal

Septum Nut

Cartridge split vent trap

EPC

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Split mode:During a split injection, a liquid sample is introduced into a hot inlet where it vaporizes rapidly. A small amount of the vapor enters the column while the major portion exits from the split/purge vent. The ratio of column flow to split flow is controlled by the user. Split injections are primarily used for high concentration samples when you can afford to lose most of the sample out the split/purge vent. It is also used for samples that cannot be diluted.

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Splitless mode:

In this mode, the purge valve is closed during the injection and remains so while the sample is vaporized in the liner and transferred to the column. At a specified time after injection, the purge valve opens to sweep any vapors remaining in the liner out the split vent. This avoids solvent tailing due to the large inlet volume and small column flow rate. Specify the purge time and purge flow rate in the inlet control table.

If you are using gas saver, the gas saver time should be after the purge time.

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Pulsed split and splitless modesThe pressure pulse modes increase inlet pressure just before

the beginning of a run and returns it to the normal value after a specified amount of time. The pressure pulse sweeps the sample out of the inlet and into the column faster, reducing the chance for sample decomposition in the inlet. If your chromatography is degraded by the pressure pulse, a retention gap may help restore peak shape.

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Inlet Types

Inlet Type Description

2. Purged-Packed Injector

It is called packed injector as it is used for packed columns analysis.Note

During injection, the sample (1ul or 2ul) is vaporized inside a glass liner (insert) in avery short period of time (milliseconds), thus, it may be called “Flash Injector”.

The type of injection mode used in a purged-packed injector is Splitless Mode.

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Purged Packed InletThis inlet is used with packed columns when

high- efficiency separations are not required. It can also be used with wide-bore capillary columns, provided that flows greater than 10 ml/min are acceptable.

If a capillary column is used and the column is defined, the inlet is pressure controlled.

If the column is not defined packed columns and undefined capillary columns), the inlet is flow-controlled.

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Purged-Packed Injector

Column Adapter

1/4” Vespel Seal

Glass Liner Sleeve

Septum Purge Weldment

Column Nut

Ferrule

Heater/SensorAssembly

“O” Ring

Septum

Insulation Cup

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Inlet Types

Inlet Type Description

3. Cool On-Column Injector

It is called on-column injector as the sample is injected and deposited directly into the column as liquid. When the sample components are thermally unstable and high sensitive is required.

Note

Most widely used applications in Environmental.

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Cool On-Column InletThis inlet introduces liquid sample directly onto a

capillary column. To do this, both the inlet and the oven must be cool at injection, at or below the boiling point of the solvent. Because the sample does not vaporize immediately in the inlet.

uses liquid CO2 or N2 to reach sub-ambient temperatures.

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Cool On-Column Injector

Heater/SensorAssembly Septum

Column Positioning Inserts

Column Nut

Ferrule

AutomatedInjection250/320

AutomatedInjection

530 Manual 200 uMFused silica needle

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Inlet Types

Inlet Type Description

4. Programmable Temperature Vaporization Injector (PTV)

It is a temperature programmable split/splitless inlet.

Note

Injection into hot or cold inlet - rapid heating/cooling.

Large volume injection capability through solvent venting for lower MDL's Less thermal breakdown.

There is two heads one is septum head with stream flow for purge septumAnd the other is septumless head which be check valve to seal the syringe entrance.

EPC pneumatics.

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Programmable Temperature Vaporization Injector

Cryo Connectio

n

Septumless Head

Septum Head

Split Vent

Liner

Heater/Thermocouple

Column Adapter

Graphpack Column Ferrule

Silver Seal

Split Nut for Inlet Adapter

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Inlet Types

Inlet Type Description

5. Volatiles Interface Injector (VI)

It is an ideal inlet for Purge & Trap, Headspace, Thermal Desorption, or other gas injection devices.

Note• Very Inert.• Very small internal volume (35ul)• Low split ratio or direct injection for high sensitivity.• EPC control from GC keyboard or ChemStation.

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Sampler Input

Trickle FlowSplit Vent

Column Connection

Volatiles Interface Injector

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Inlet Column

Mode SampleConc.

comments Sample to column

Split/Splitless

Capillary

SplitPulsed split

SplitlessPulsed splitless

HighHigh

LowLow

May be useful with large inj.

Useful with large inj.

Very littleVery little

AllAll

Cool on-column

Capillary

n/a Low or labile

Minimal discrimination and decomposition

All

Purged packed

PackedLarge capillary

n/an/a

AnyAny Ok if resolution not

critical

AllAll

Program temperature vaporization

Capillary

SplitPulsed splitSplitlessPulsed splitlesssolvent

HighHighLowLowLow Multiple inj. Conc.

Analytes and vent solvent

Very littleVery littleAllAllMost

Volatiles interface

capillary

DirectSplitSplitless

LowHighlow

Lowest dead volumeMax flow – 100ml/min

AllVery littleall

An Overview of Inlets

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Septum Purge

The septum purge line is near the septum where the sample is injected. A small amount of carrier gas exists through this line to sweep out any bleed. Each inlet has a different septum purge flow. The GC automatically sets the purge flow for EPC inlets, but you can measure it from the septum purge vent at the flow manifold if you like.

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Inlet Carrier Septum Purge

(ml/min)

1. Split/Splitless

2. Purged-Packed

3. Cool On-Column

4. Programmed Temp.

Vaporization (PTV)

5. Volatiles Interface

(VI)

He, N2, Ar/5%Me

H2

All

He, N2, Ar/5%Me

H2

He, N2, Ar/5%Me

H2

He, N2, Ar/5%Me

H2

3

6

1 to 3

15

30

3

6

3

6

Septum Purge Flows

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B. Valves

Used for quantitative analyses of gas mixtures. Different gas sample loops are available and range from 250ul to 50ml.

There are many valving configurations to accommodate each kind of gas analyses requirements.

Four-Port Six-Port Eight-Port Ten-Port Valves Valves Valves Valves

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The END

Produced By Mohamed Salama